Automatic nut tapper



Dec. 19, 1967 HARALAMPlEV ET AL 3,358,306

AUTOMATI C NUT TAP PER 5 Sheets-Sheet 1 Filed Aug. 17, 1965 INVENTORS Iliya S. Haralampiev Assen A. Valev Aitorn ey Dec. 19, 1967 l. s.HARALAMPIEV ET AL 3,358,306

AUTOMATI C NUT TAP PER 3 Sheets-Sheet Filed Aug. 17, 1965 plev Va/evINVENTORS.

1.5. Hare/am Assen A.

g) n 4% 4W Attorn ey Dec. 19, 1967 Filed Aug. 17, 1965 muumnmm11mm I. s.HARALAMPIEV ET AL 3,358,306

AUTOMATI C NUT TAP PER 5 Sheets-Sheet 3 Fig.6

INVENTORS: Iliya S.Hara/ampiev BY Assen A.V=1/ev 6 ss Ka K0 AttorneyUnited States Patent 3,358,306 AUTOMATIC NUT TAPPER Iiiia StoilkovHaralarnpiev and Assen Atanassov Valev,

Sofia, Bulgaria, assignors to Darjavno Stopansko ObedineuieMetaloobrabotvashti i Darvoobrabotvashti Masiiini i iustrumenti, Sofia,Bulgaria, a corporation of Bulgaria Filed Aug. 17, 1965, Ser. No.480,461 Claims priority, application Bulgaria, Aug. 17, 1964,

Claims. for. -433 ABSTRACT OF THE DISCLOSURE Our present inventionrelates to a machine for the cutting of female threads on a tubularworkpiece, such as a nut.

Short tapping tools suitable for this purpose are generally gripped atone end by a chuck and inserted at the other end into a bore of theworkpiece to be threaded.

In many instances it is convenient to use a tapping tool of an overalllength substantially exceeding the length of its effective cuttingportion, i.e. the tooth part of the tool, in order to provide anextension on which successive nuts or similar workpieces can beaccumulated before the machine is arrested to permit the removal of thefinished workpiece. In practice, however, it has heretofore not beenpossible to use such elongated tapping tools because of the vibrationswhich the unsupported working end of the tool would experience inoperation.

It is, therefore, an object of our present invention to provide meansfor facilitating the use of such elongated tapping tools in a threadingmachine of the character set forth, thereby enabling the machine to berun without interruption through a succession of work cycles.

Another object of this invention is to provide means for steadying atapping tool in a nut-threading or similar machine to improve thequality of the products.

In accordance with this invention we provide, as part of athread-cutting machine, an axially fixed holder adapted for clampingengagement with an end of a tapping tool, advantageously a tool having acurved rear extremity whereby the tool can be more positively located inthe holder without the use of special gauges; axially spaced from thisholder, at a location beyond the opposite or Working end of the engagedtool, a gripper is axially reciprocable between a normal position remotefrom the tool and a working position in which the gripper positivelyengages the proximal or forward end of the tool which for this purposeis being given a suitable polygonal or other noncircular shape. An inletlocated between the front end of the tool and the normal position of thegripper allows for the introduction of a workpiece into the interveningspace, this workpiece being then advanced into contact with thethread-cutting portion of the tapping tool by a pusher which yieldablyentrains the gripper, eg through the intermediary of a compressionspring, in an initial stage of its Working stroke. The tapping tool,accordingly, should have a smooth-surfaced front portion ahead of itsthread-cutting portion, this front portion being long enough toaccommodate the workpiece (or several juxtaposed workpieces to bethreaded concurrently) 3,358,306 Patented Dec. 19, 1967 while thegripper advances into contact with the tool; after this contact has beenmade, and with the tool thus steadied at both ends, the pusher furtheradvances the workpiece or workpieces over and beyond the threadcuttingportion of the tool until they arrive at the rearward extension thereof.

During the thread-cutting operation proper, relative rotation must beimparted to the workpiece, on the one hand, and the tool-engaging holderand gripper, on the other hand, by a driving mechanism properlysynchronized with the forward motion of the pusher. To this end, theworkpiece is peripherally engaged by a sleeve, e.g. of hexagonalprofile, which is either stationary or driven and which controls theangular position of the workpiece in the region of the thread-cuttingportion so as to secure the workpiece against rotary entrainment by thedriven tool or to rotate the workpiece around the stationary tool.

In either case, according to a more specific feature of our invention,the two tool-engaging elements (holder and gripper) are advantageouslyinterconnected by a limitedly yieldable coupling enabling only slightrotation of the two ends of the tool under severe torsional stresses. Arestrictive coupling of this type may include a differential gear trainwhose housing is either fixed or directly coupled to the drive means,depending on whether rotation is to be imparted to either the nut or thetool. The main drive, which rotates the workpiece or the tool, and/ orthe pusher drive, which is synchronized therewith, may be equipped withconventional speed-changing means to permit changes in the pitch of thethread to be cut. One of these drives may also be reversible,independently of the other, to facilitate switching from right-hand tolefthand threads or vice versa.

The invention will be described in greater detail with reference to theaccompanying drawing in which:

FIG. 1 is a diagrammatic view of a machine embodying our invention;

FIG. 2 is a cross-sectional view taken on the line II-11 of FIG. 1;

FIG. 3 is a view similar to FIG. 1, showing a modified machine embodyingthe invention;

FIG. 4 is a cross-sectional view taken on the line IVIV of FIG. 3;

FIG. 5 is an enlarged plan view of a tapping tool adapted to be used inthe machine of FIG. 1 or 3, along with part of a clamp therefor; and

FIG. 6 is a side view of the tool-holding clamp shown in FIG. 5.

In FIG. 1 we have shown a motor 10 driving, via a transmission 11, ashaft 12 which powers, via a gear 13, a differential housing 14 havingtwo output shafts 15 and 16. Shaft 15 is coupled, by way of bevel gears16, 17 and an intermediate shaft 18, with a drive shaft 19 having a toolholder 20 secured thereto. This tool holder is clamped, in a manner morefully described hereinafter in connection with FIGS. 5 and 6, to atapping tool 21 having a curved rear extremity 21a and an elongated body21b in line with shaft 19, this body including a thread-cutting portion210, a forward extension 21d of substantially the same length as workingportion 21c, and a tip 21e of polygonal (e.g. hexagonal) outline.

Output shaft 16 is connected via bevel gears 22, 23 and a transverseshaft 24 with a splined drive shaft 25 which is telescoped in andmatingly engaged by a tubular extension shaft 26 terminating in agripper 27 with a socket-shaped extremity having a polygonal profilecomplementary to that of the front end 21c of tapping tool 21. Shaftassembly 25, 26 is rotatably and slidably mounted, via bearings 28, inan axially reciprocable tubular pusher member 29 whose reciprocation iscontrolled by a continuously rotating cam 30 via a follower 31. Themeans for driving the cam 30 in step with the shafts 19 and 26 includebevel gears 32, 33 by which the torque of shaft 12 is transmitted firstto an auxiliary shaft 34- and thento another auxiliary shaft35 which is"conpled by way of-aspeed -changer.36-and areversing gear 37 withardrive shaft 38 bearing aworm 39 in mesh'with -a worm-gear 40 on .theshaft of-cam- 30. The forward stroke of the reciprocation ofrpusher 29,i.e. the beginning of its leftward motion from the illustrated" normalposition thereof, is communicated -tothe telescope-shaft 26 'andgripper27 through a compression spring 41 interposed betweenshaft :26 and;pusher 29. In this normal -position, a space-exists betweenpusher 29and: gripper -27, on the one-hand; and the end:21e of tapping tool 21,on the other hand, this space being aligned with a hopper 42" from whichone or more workpieces, such as pairs of juxtaposed nut blanks -43, canbefed into the gap between the pusher assembly and the tool. Theworkpieces 43 are received in-a sleeve'44 which, in theregion-surrounding thetool portions 210 and-21d, is of polygonal(preferably-hexagonal) profile to match the outline of .the workpieces43v wherebyv the latter areangularly irn mobilized. upon being advancedinto the sleeve 44 by the steadily moving pusher .29.

LCam 30 has alower dwell '30 of a radius rcoore- .sponding to .thedistance between the-end of tool section .21d-and the gripper 27 in itsnormalwithdrawn position,'thusa distance greater than the combined'widthof the nuts 43 persent .in the gap between the tool and'the r..gripper.The. cam-alsohas a higher dwell 30 of radius R corresponding to thedistance measured from the end of. pusher 29 (in its. normal withdrawnposition) to a point beyond tool portion 21c- In operation, therefore,,pusher. 29.advances the workpieces first into a position just aheadofthe thread-cutting portion 210 of tool 21 within the sleeve 44;simultaneous1y,'the gripper 27 entrained-by the spring.41 has matinglyengaged-the tip 21e of the-tool so that both. ends ofthe toolare-positively ..driven with substantially. equal torques from .theoutput of differential 14. The pusher 29 then continues its. advance.until the tool-has passed the threading portion" 210 and has landed onthe storage portion 2112; during this -.-part of thestrokethe spring 41.is compressed without any further advancev ofuthe. engagedgripper 27;Finally, the pusher assembly 2629-.is retracted duringthe return strokeof the cam drive and the parts are restored-to their normal positionillustrated in- FIG. 1.

.-After .the maximum permissible number of workpieces have accumulatedon the .stem.-21b.of the tapping tool 21, .the machine is stopped and:theclamplfl is opened to enable removal of the tool and recovery of:theworkpieces held thereon. To this end, the clamp may consist oftwoparts 20'a,l'20b (FIGS. and 6) held together bybolts20c,-clamp.half.20a--being rigid with' shaft 19.

'The. system of FIG. 3 is generally similar to that of 'FIG. 1'. andidenticalnumerals, supplemented: by a "1 -.in. the.:position of thehundredsdigit, have been used-to identify analogous elements which forthemost partneed .not be further described. In contradistinction to thepreceding embodiment, however, sleeve 144 is now positively coupledwiththe drive shaft 112 of motor 110* whereas -..the housingofdifi'erential114, whose outputshafts 115, 116 are coupled asbeforewith holder-shaft 119and gripper. shaft 125,..is-held stationary. A'slight' relative rotation of tool ends 21a and 21e-is thus possibleunder tor sionalsstress'The polygonally profiled sleeve 144 extends onlyslightly forwardly-of. theregion of tool por- .tionl21candadjoins astationary sleeve 145 of circular C1'0SS-S6CIlOI1 whichreceivestheworkpieces 43 from hopz per 142. .Sleeve 144 is drivendirectly fromshaft 112 via -a-spur gear 146-in mesh with gear 114 and keyed tothesleve;=gear 146, -'in turn, drives a gear' 147 keyed to shaft-135which is coupled wite worm-gear shaft 138 "viaspeed-changingandreversing gears'136, 137. The enztrance end of sleeve 144 is suitablyfiaredto receive the oncoming nuts from sleeve 145.

Apart from the kinematic reversal as between the tool and theworkpieces, the operation of the machine of FIG. 3 is analogous to thatof the machine of FIG. 1.

We claim:

1. In-a machine for internally threading blanks to form nuts and"havinga pair of axially aligned spindles provided at confronting endswith gripper means and adapted --to engage nut blanks fed between. them,one of the spindles carrying a tap for threading a nut blank upon itsengagement by the spindles, and common drive means connected with thespindles at theirextremities'remote from their confronting ends forrotating said spindles jointly, the improvement which comprisestorque-equalizing differential means in said drive means between saidspindles for affording at'least limited relative rotation thereof andequalizing the torque applied thereto by said A drive means.

2. A machine for the cutting of female threads in tubular workpieces,comprising axially fixed holder means for clamping an end of a tappingtool; grippermeans axially spaced from said holder'means at a locationbeyondthe for entrainment thereby in the initial phase of a workingstroke of said pusher means'whereby said gripper means is brought intopositive engagement with said opposite end of the tapping tool duringaxial displacement'of said workpiece over a'distance exceeding thelengthof said space; sleeve means peripherally engageable with saidworkpiece'for controlling the angular.positionthereof in the region ofsaid thread-cutting. portionyfirst drive means for relatively rotatingsaid'holder means. and said sleeve means while maintaining said grippermeans 'in substantially fixed angular alignmentwith said'holder meanswhereby said tapping toolis subjectedto substantially equal torsionalstresses at both endspand second drive means synchronized with saidfirst drive means for reciprocating said pusher-means whereby saidworkpiece isaxially advanced in timed relationship with its rotationrelative to the tapping tool,'said first drive-means including a'firstshaft fixedly secured to said holder means, a second shaft.positively'connectedwith said gripper 'means including a differential, geantrain,and coupling means interconnecting said shafts with freedom of limitedrelative rotation.

3. A machine as defined in claimZgwher'eiu said holder means comprises aclamp provided'with acurved channel for accommodating a bent extremityof said tapping tool.

4. A machine as defined in claim 2 wherein one of said drive means isprovided with rotation-reversing means.

'5. A machine as-defined in clairn2 wherein said second drive meansincludes cam meansfor axially advancing said pusher. means in aninitial. phase suificiently to engage said gripper means-with saidtapping 'tool, thereafter holding said pusher means stationary in anintermediate phase wherein saidworkpiece rests on'a smooth-surfacedforward portion of said tool, and finally advancing-said pusher means tomove the workpiece past said thread-cutting portion in a terminal phaseof said working stroke.

References Cited UNITED STATES PATENTS 922,248 5/1909 'Bilgram 10.133l,ll3,444 10/1914 Johnston 10%129 1,944,653 1/1934 Clouse 10-139 FRANCISS. HUSAR, Primary Examiner.

1. IN A MACHINE FOR INTERNALLY THREADING BLANKS TO FORM NUTS AND HAVINGA PAIR OF AXIALLY ALIGNED SPINDLES PROVIDED AT CONFRONTING ENDS WITHGRIPPER MEANS AND ADAPTED TO ENGAGE NUT BLANKS FED BETWEEN THEM, ONE OFTHE SPINDLES CARRYING A TAP FOR THREADING A NUT BLANK UPON ITSENGAGEMENT BY THE SPINDLES, AND COMMON DRIVE MEANS CONNECTED WITH THESPINDLES AT THEIR EXTREMITIES REMOTE FROM THEIR CONFRONTING ENDS FORROTATING SAID SPINDLES JOINTLY, THE IMPROVEMENT WHICH COMPRISESTORQUE-EQUALIZING DIFFERENTIAL MEANS IN SAID DRIVE MEANS BETWEEN SAIDSPINDLES FOR AFFORDING AT LEAST LIMITED RELATIVE ROTATION THEREOF ANDEQUALIZING THE TORQUE APPLIED THERETO BY SAID DRIVE MEANS.